The present invention relates to a novel and improved press-contact type interconnector of elongated form or, more particularly, to an interconnector used, for example, as sandwiched between a printed circuit board for electronic operation circuit and a circuit board bearing a functional device to establish electric connection therebetween.
It is a common practice that an electronic functional device such as a liquid display unit, electroluminescence display unit or the like is mounted on a circuit board for the operation thereof with a press-contact type interconnector of elongated form sandwiched therebetween to obtain electric connection between them, such an interconnector being electrically conductive only in the direction perpendicular to the longitudinal direction thereof to give an electric connection between the contacting terminals oppositely positioned on both sides of the interconnector.
Interconnectors of this type are described, for example, in U.S. Pat. Nos. 3,795,037 and 3,862,790, Japanese Patent Disclosure No. 53-147991 and others. The interconnectors disclosed there are formed of an elongated rod member made of an electrically insulating rubbery elastomer and a multiplicity of linear or fibrous bodies having electroconductivity embedded in the insulating rubber matrix approximately in alignment in one direction perpendicular to the longitudinal direction of the rod member throughout its length.
One of the problems in the interconnectors of the above described type is that, when the interconnector is sandwiched between two circuit boards with a pressure sufficient to obtain reliable electric connection between them, the rubber matrix of the rod member becomes extended or stretched perpendicularly to the direction of compression, e.g. in the longitudinal direction of the rod member in proportion to the compression by the pressure which is perpendicular to the plane of the circuit boards to be electrically connected owing to the relatively large Poisson's ratio of the rubbery material. This longitudinal extension of the rod member necessarily leads to the decrease in the density of the linear or fibrous conductive bodies or to the disorder in the electric contact between the interconnector and the circuit board. This undesirable phenomenon is most remarkable in the end portions of the elongated interconnector. An attempt to avoid the above problem by increasing the clamping pressure at the end portions is unsuccessful due to the possible unevenness of the contacting condition in the intermediate portions.
The interconnector described in Japanese Patent Disclosure 52-107566 is improved in respect of the above problem but it is never satisfactory with a requirement of very large compression stress in mounting to obtain uniform contacting because each of the linear conductive bodies in texture is bent in the reverse direction to the neighboring ones.